const foo = new Promise(async (resolve, reject) => {
  readFile('foo.txt', (err, result) => {
    if (err) {
      reject(err);
    } else {
      resolve(result);
    }
  });
});

const result = new Promise(async (resolve, reject) => {
  resolve(await foo);
});

new Promise(async function foo(resolve, reject) {})
new Promise(async (resolve, reject) => {})
new Promise(((((async () => {})))))